7) 鉄筋コンクリート格子梁の塑性的性質について

Abstract

In case we study on a reinforced concrete framework, we have to investigate on the influences of the plasticity of reinforced concrete members on the mechanical properties of that frame. It is necessary both in utilizing them in practical purpose and in clarifying the ultimate strength mechanism of a reinforced concrete frame. On this subject, some theoretical works have been carried out today, but we have very few experimental studies. In this paper, the auther investigated experimentally on the plastic mechanical properties of reinforced concrete grid-frameworks subjected to the concentrated load perpendicularly at the center of their plane. The experiments was carried out by using ⊞-type and ⊞-type models. The ultimate strength, collapse mechanism, stress distribution and deformation of the frames are examined both experimentally and theroretically. The result showed the following fundamental properties on the plastic behaviour of reinforced concrete grid-frameworks. 1. Except the torsional failure of a member of the frame takes place, ultimate strength theory based on the perfect plasticity of reinforced concrete flexural members gives almost exact answer for the ultimate strength of a reinforced concrete grid-framework, in which we must take it into account that bending bearing capacity of a reinforced concrete beam is sometimes much reduced under the combined action of bending and orstional moment together. 2. On the torsional failure of a reinforced concrete combined-stress-member of torsion and bending, it seemed that the place and the pattern of the torsional crack is governed by the existing bending cracks. As to the torsional strength of that kind of members we could not get enough data. 3. General aspect of plastic deformation and plastic stress distribution of the frame is given by applying the perfect plastic theory. 4. Rigidity reduction of a member, which is caused by cracks, sometimes causes much change of stress distribution in the frame. This rigidity reduction of a member, by one bending crack, was also observed for torsion at the same time for bending.